Ceramic coating bonded to iron member

Abstract

A ceramic coating bonded to an iron tubular member comprising a bonding layer formed on a surface of the iron tubular member by a reaction of an iron tubular oxide layer of the iron tubular member and a silicate; and an iron oxide diffusion-preventing layer produced from fine metal oxide particles or an organometallic binder by firing on a surface of the bonding layer. The ceramic coating may further comprises an oxidation-preventing layer, a heat-insulating layer, a refractory layer or a thin dense protective layer. It may be produced by coating the surface of the iron tubular member with a silicate binder to form a layer which is then converted to a bonding layer by a heat treatment in a steam atmosphere; coating the surface of the bonding layer with fine metal oxide particles or an organometallic binder to form an iron oxide diffusion-preventing layer; and after curing and drying firing the resulting ceramic coating in an atmosphere having an oxygen partial pressure of 10 mmHg or less.

We claim: 
     
       1. A coated iron tubular member comprising a first layer formed on a surface of said iron tubular member by a reaction of an iron oxide layer of said iron tubular member and a silicate; and an iron oxide diffusion-preventing layer formed on a surface of said first layer, said iron oxide diffusion preventing layer being produced from a material selected from the group consisting of fine metal oxide particles and organometallic compositions, which material does not form a low-melting point product with iron oxide, by firing said material on the surface of said first layer. 
     
     
       2. The coated iron tubular member according to claim 1, further comprising a thin, dense protective layer composed of an inorganic material and/or an organometallic material on a surface of said iron oxide diffusion-preventing layer. 
     
     
       3. The coated iron tubular member according to claim 1, further comprising an oxidation-preventing layer comprising inorganic flaky particles consolidated by firing to have a cross-linked laminate structure on a surface of said iron oxide diffusion-preventing layer. 
     
     
       4. The coated iron tubular member according to claim 3, wherein said inorganic flaky particles are those produced by crushing natural or artificial mica, thin glass or inorganic hollow particles. 
     
     
       5. The coated iron tubular member according to claim 3, further comprising a thin, dense protective layer comprised of an inorganic material and/or an organometallic material on a surface of said oxidation-preventing layer. 
     
     
       6. The coated iron tubular member according to claim 3, further comprising a heat-insulating layer formed by firing a heat-insulating material mainly composed of inorganic hollow particles on a surface of said oxidation-preventing layer. 
     
     
       7. The coated iron tubular member according to claim 6, further comprising a thin, dense protective layer composed of an inorganic material and/or an organometallic material on a surface of said heat-insulating layer. 
     
     
       8. The coated iron tubular member according to claim 6, further comprising a refractory layer formed by firing a refractory material mainly composed of inorganic particles on a surface of said heat-insulating layer. 
     
     
       9. The coated iron tubular member according to claim 8, further comprising a thin, dense protective layer composed of an inorganic material and/or an organometallic material on a surface of said refractory layer. 
     
     
       10. The coated iron tubular member according to claim 3, further comprising a refractory layer formed by firing a refractory material mainly composed of inorganic particles on a surface of said oxidation-preventing layer. 
     
     
       11. The coated iron tubular member according to claim 10, further comprising a thin, dense protective layer composed of an inorganic material and/or an organometallic material on a surface of said refractory layer. 
     
     
       12. The coated iron tubular member according to claim 1, further comprising a heat-insulating layer formed by firing a heat-insulating material mainly composed of inorganic hollow particles on a surface of said iron oxide diffusion-preventing layer. 
     
     
       13. The coated iron tubular member according to claim 12, further comprising a thin, dense protective layer composed of an inorganic material and/or an organometallic material on a surface of said heat-insulating layer. 
     
     
       14. The coated iron tubular member according to claim 12, further comprising a refractory layer formed by firing a refractory material mainly composed of inorganic particles on a surface of said heat-insulating layer. 
     
     
       15. The coated iron tubular member according to claim 14, further comprising a thin, dense protective layer composed of an inorganic material and/or an organometallic material on a surface of said refractory layer. 
     
     
       16. The coated iron tubular member according to claim 1, further comprising a refractory layer formed by firing a refractory material mainly composed of inorganic particles, on a surface of said iron oxide diffusion-preventing layer. 
     
     
       17. The coated iron tubular member according to claim 16, further comprising a thin, dense protective layer composed of an inorganic material and/or an organometallic material on a surface of said refractory layer. 
     
     
       18. The coated iron tubular member according to claim 1, wherein said iron tubular member is part of exhaust equipment. 
     
     
       19. A layered product for use in a high-temperature oxidizing atmosphere comprising: an iron member having a surface;   a first layer formed on said iron member surface by a reaction of an iron oxide layer on said iron member surface and a silicate, said first layer having a surface; and   an iron oxide diffusion preventing layer formed on said surface of said first layer, said iron oxide diffusion preventing layer being formed by firing a material which does not form a low-melting point product with iron oxide.   
     
     
       20. The layered produce as in claim 2 wherein said iron oxide diffusion preventing layer is produced from a material selected from the group consisting of metal oxide particles and organometallic compositions by firing said material on said first layer surface.